实海暴露黄铜脱锌腐蚀行为及抑制脱锌机理研究

采用金相－扫描电子显微镜和电子探讨Ｘ射线能谱成分分析方法研究了黄铅实海暴露脱锌腐蚀特征及抑制机理。通过对长期实海暴露试样的腐蚀产物和合金基体进行成分分析及形貌观察,研究表明加Ａｓ的Ｈ６８Ａ黄铜晶界优先发生脱锌腐蚀,而加Ｓｎ后,由于-了晶界,　大大提高了单相α黄铜(HSn70-1A)的耐蚀性能.而对双相HSn70-1A黄铜,添加Sn,可在一定程度上抑制脱锌,但并不足以阻止腐蚀沿β相之间的α相晶界的连通.     

黄铜脱锌腐蚀行为特征的电子探针分析

黄铜脱锌作为一种选择性腐蚀现象给生产和生活带来很大的安全隐患.添加一些合金元素可以改善脱锌现象,改善黄铜的耐腐蚀性能.使用岛津电子探针EPMA测试了某种含锡的黄铜,表征了其脱锌腐蚀行为特征,以及添加的合金元素锡的分布特征及其在提高黄铜耐腐蚀性能方面的作用,即脱锌腐蚀首先发生在暴露于基体表面的β相晶粒,然后通过晶界和相界...     

Electrochemical corrosion behaviour of Bi-11Ag alloy for electronic packaging applications

This study investigated the electrochemical corrosion properties of the solders for die-attach applications in 3.5% NaCl solution. Compared with Pb-5Sn and Zn-40Sn, Bi-11Ag exhibited higher corrosion potential and relatively low corrosion current density. The ductile Ag-rich phase which dispersed in the Bi matrix was able to accommodate the stress arising from the formation of a passive layer and contributed to the two-stage passivation. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirm that the corrosion products comprised BiOCl, Bi₂O₃ and AgCl.     

Stress corrosion cracking and selective corrosion of copper-zinc alloys for the drinking water installation

Despite a generally good corrosion resistance to tap and industrial water, many brass taps and fittings have failed in the past by stress corrosion cracking (SCC) and selective corrosion (dezincification or preferred removal of a phase). The experimental investigations of the present study clarify the influence of the ammonia concentration on the two types of corrosion. Notched specimens made of the alloys CuZn39Pb3, CuZn40Pb2, CuZn37, CuZn36Pb2As and CuZn21Si3P are polarized anodically in pure tap water and tap water with realistic ammonia concentrations (15 and 30 ppm) under a simultaneous mechanical loading condition. The influence of stress and of the third alloying elements lead and arsenic are investigated and evaluated. The experiments show that the ammonia additions significantly increase the risk of dezincification of the α-β-brasses. The arsenic in the CuZn36Pb2As alloy avoids dezincification, but enhances the risk of SCC. The rate of selective corrosion and SCC consistently increases with increase in tensile stress.     

Einfluß der Zusammensetzung von Messinglegierungen auf die Entzinkung und interkristalline Korrosion in Ammoniumchloridlösung

Influence of the composition of brass on dezincification and intercrystalline corrosion in ammonium chloride solutions The intercrystalline corrosion of As-containing α-brass is not restricted to a defined brass composition but is found also with brass types containing, in addition, AL and Sn. In the case of two-phase alloys of this type the β-phase is preferentially corroded, in Particular when the brass contains As and the β-phase forms a coherent network. On the basis of the results obtained a hypothesis has been derived as to mechanism the partial processes; this hypothesis is confirmed by result obtained with macroelements of As-containing and As-free brass. According to this hypothesis the intercrystalline corrosion of α- brass can be ascribed to the inhibition by As of the dezincification, so that no regions more anodic than grain boundaries are formed. This is why the boundaries are attacked preferentially.     

Effect of rapid solidification on the microstructure and corrosion behaviour of Al-Zn-Mg based material

The corrosion behaviour of Al-5Zn-3Mg-0.6Cu-0.8Zr-0.25Cr-0.15Ni-0.15Ti alloys, produced by traditional and powder technologies, with similar thermo-mechanical treatments, in 3% sodium chloride solution, has been examined by electrochemical methods, scanning electron microscopy, transmission electron microscopy and X-ray microanalysis. The alloys reveal similar precipitation but of different shape, size and distribution; further, both alloys experience localized corrosion. Copper-rich precipitates initiate the dissolution of surrounding particles, enriched in Zn and Mg. As a result, the surface is enriched with other alloying elements after a full polarisation run. Cast material has lower corrosion properties because of the higher heterogeneity of the structure. The structure heterogeneity of the cast material involves a more non-uniform distribution of the precipitates, larger Zn- and Mg-rich particles, and depletion of the matrix and areas around the precipitates by alloying elements compared with the powder material.     

Electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys in chloride containing aqueous solution

The electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys was investigated in 3.5% NaCl solution by using potentiodynamic polarization techniques. The results obtained from polarization studies revealed that there was a negative shift in the corrosion potential with increase in Ga content from 0.02 to 0.2 wt% in the Sn-8.5Zn-0.05Al-XGa alloy. These changes were also reflected in the corrosion current density (I_corr) value, corrosion rate and linear polarization resistance (LPR) of the four element alloy. However, for Sn-3Ag-0.5Cu alloy a significant increase in the corrosion rate and corrosion current density was observed as compared to the four element alloys. SIMS depth profile results established that ZnO present on the outer surface of Sn-8.5Zn-0.05Al-0.05Ga alloy played a major role in the formation of the oxide film. Oxides of Sn, Al and Ga contributed a little towards the formation of film on the outer surface of the alloy. On the other hand, Ag₂O was primarily responsible for the formation of the oxide film on the outer surface of Sn-3Ag-0.5Cu alloy.     

Diffusion mechanism of dezincification in double-phase brass exposed to seawater

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Improving the shear strength of Sn–Ag–Cu–Ni/Cu–Zn solder joints via modifying the microstructure and phase stability of Cu–Sn intermetallic compounds

This study focuses on the correlation between high-speed impact tests and the interfacial reaction in Sn-3.0Ag-0.5Cu-0.1Ni/Cu (wt%) and Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints. Adding Ni into the Sn–Ag–Cu solder alters the interfacial morphology from scallop type to layer type and exhibits high shear strength after reflow in both solder joints. However, the shear strength of Sn-3.0Ag-0.5Cu-0.1Ni/Cu solder joints degrades significantly after thermal aging at 150 °C for 500 h. It is notable that Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints still present higher shear strength after aging at 150 °C. The weakened shear strength in Sn-3.0Ag-0.5Cu-0.1Ni/Cu solder joints is due to stress accumulation in the interfacial (Cu,Ni)₆Sn₅ compound induced by the phase transformation from a high-temperature hexagonal structure (η-Cu₆Sn₅) to a low-temperature monoclinic structure (η'-Cu₆Sn₅). However, doping small amounts of Zn into (Cu,Ni)₆(Sn,Zn)₅ can inhibit the phase transformation during thermal aging and maintain strong shear strength. These experiments demonstrate that Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints can act as a stable connection in the micro-electronic packaging of most electronic products at their average working temperatures.     

Die Korrosion von Messing in Ammoniumchloridlösungen

Corrosion of brass in ammonium chloride solutions The corrosion behaviour of brass (Cu77Zn21A/2, with and without addition of As) has been investigated in 0.01 to 1 M ammonium chloride solution of PH 4 and 2, and in solutions 1 M in chloride ion, with variable Na⁺ and NH⁺₄ concentrations (total concentration 1 M in each case), at pH 4 and 2. While arsenium-free brass was attacked by dezincification in most cases, intercrystalline corrosion was found on As-containing brass. The latter type of corrosion is found already at As contents as low as 0.01%. In a medium 1 M in chloride ion intercrystalline corrosion is found at PH 2, irrespective of the ammonium ion concentration, while at PH 4 intercrystalline corrosion is found only at higher ammonium ion concentrations (practically 1 M). The intercrystalline corrosion was found to be due to the segregation of Zn and As respectively at the grain boundaries and to the influence of As on the stability of the CuCl^?₂ formed by the anodic reaction. The influence of the solution composition on the progress in time of the intercrystalline corrosion is explained.     

Electrochemical studies of the corrosion of some Cu-Zn alloys in organic acids

The electrochemical corrosion parameters, e.g. corrosion current density, corrosion rate and polarization resistance, of 63Cu-37Zn, 70Cu-30Zn and 58.81Cu-39.53Zn-1.66Pb alloys were measured in aqueous solutions of weak organic acids (oxalic, tartaric and succinic acid). Three techniques were used for these measurements, namely potentiodynamic, Tafel plot and polarization resistance using the model 350A-PARC corrosion measurement system. The effect of acid concentration and temperature on the corrosion parameters of such alloys is discussed.     

Dezincification studies of some copper based alloys

Abstract

The corrosion resistance of low zinc yellow brass showed significant improvement with increasing additions of aluminium to the alloy, as evidenced by data on corrosion rates obtained from corrosion currents, amounts of zinc released, and loss in weight of samples. All of the alloys in the permanent mould cast condition showed greater resistance to dezincification than did sand cast alloys. Low zinc yellow brass and high zinc yellow brass showed the highest resistance to dezincification as evidenced by data on pit depths.     

液-固相轧制法生产Al-8Sn-2.5Si-2Pb-0.8Cu-0.2Cr/钢复合轴瓦带的组织与性能

采用液-固相轧制复合法生产Al-8Sn-2．5Si-2Pb-O．8Cu-O．2Cr／钢复合轴瓦带．通过表面处理后的钢带能很好地与Al合金液润湿并产生冶金结合，且结合强度高、界面牢固．同时，液-固相轧制冷却速度大，金相观察表明Al合金为细晶的显微组织；电子探针观察表明：Si，Sn，Pb和Cr等元素在组织内分布均匀，有利于提高轴瓦性能．     

Preparation, deformation, and failure of functional Al-Sn and Al-Sn-Pb nanocrystalline alloys

Changes in the structure, hardness, mechanical properties, and friction coefficient of Al-30% Sn, Al-15% Sn-25% Pb, and Al-5% Sn-35% Pb (wt %) alloys subjected to severe plastic deformation by equal-channel angular pressing (with a force of 40 tonne) and by shear at a pressure of 5 GPa have been studied. The transition into the nanocrystalline state was shown to occur at different degrees of plastic deformation. The hardness exhibits nonmonotonic variations, namely, first it increases and subsequently decreases. The friction coefficient of the Al-30% Sn, Al-15% Sn-25% Pb, and Al-5% Sn-35% Pb alloys quenched from the melt was found to be 0.33; the friction coefficients of these alloys in the submicrocrystalline state (after equal-channel angular pressing) equal 0.24, 0.32, and 0.35, respectively. The effect of disintegration into nano-sized powders was found to occur in the Al-15% Sn-25% Pb, and Al-5% Sn-35% Pb alloys after severe plastic deformation to ? = 6.4 and subsequent short-time holding.     

Structural and elastic properties of eutectic Sn-Cu lead-free solder alloy containing small amount of Ag and In

Sn-Cu alloys have been considered as a candidate for high temperature lead-free microelectronic solders. In the present study, the change in microstructure, attenuation and elastic behavior associated with alloying of Ag and/or In into the eutectic Sn-Cu solder alloy system have been evaluated. The study involved measurements of longitudinal and shear wave velocities, attenuation, hardness, bulk and shear moduli, Young's and Poisson's ratio. The results of attenuation show that a clear attenuating effect in the ternary Sn-Cu-Ag and Sn-Cu-In alloys is realized, whereas the quaternary Sn-Cu-Ag-In solder displays an obscure attenuating effect. The obscure effect is mainly attributed to the competition for In between Sn and Ag, which results in weak interface formed between intermetallic compounds (IMCs) and β-Sn matrix. Likewise, Poisson's ratio results indicate that its value decreases with increasing the elastic moduli and ultrasonic velocities of Ag and In-containing alloys. The analyzed enhanced ductility of Sn-0.7Cu and Sn-0.7Cu-2In alloys and brittleness of Sn-0.7Cu-2Ag and Sn-0.7Cu-2Ag-2In alloys were rationalized on the basis of Poisson's ratio and the quotient of shear modulus to bulk modulus (Pugh's ratio). Microstructural analysis revealed that the origin of change in the elastic properties of the ternary and quaternary alloys is ascribed to smaller β-Sn dendrite grain dimensions and formation of new IMCs in the ternary and quaternary alloys.     

制备双金属复合材料的半固态成型法的研究

以半固态合金Sn-15%Pb和Pb-30%Sn为研究对象,探索应变诱发熔体激活(SIMA)触变锻造制备双金属复合材料的可行性。实验结果表明,半固态金属液体以层流方式流动;复合材料中的球状初晶仍维持各自成分性质和形貌特征;两种半固态合金的液相混合物限制在复合界面下的薄层中;原料的氧化皮在成形过程中撕裂,界面处没有氧化物富集层。     

挤压铸造Al-Cu-Mn和Al-Zn-Mg-Cu合金耐腐蚀性能研究

采用酸性盐雾试验,对Al-4.5Cu-0.8Mn和Al-7.3Zn-2.9Mg-1.9Cu 2种挤压铸造合金的耐腐蚀性能进行了对比研究.结果表明,在盐雾腐蚀过程中,随着腐蚀时间的延长和压力的增大,两种合金的耐腐蚀性能都出现了一定程度的下降.前者的腐蚀是由分布于枝晶间和晶界处的T(Al12CuMn2)和θ(Al2Cu)相溶解引起的,后者的腐蚀是由合金中η相的优先溶解,以及沿晶界分布的S相边沿的(Al)基体溶解所致;前者的耐腐蚀性能明显优于后者.     

Development of high strength Sn-0.7Cu solders with the addition of small amount of Ag and In

Nowadays, a major concern of Sn-Cu based solder alloys is focused on continuously improving the comprehensive properties of solder joints formed between the solders and substrates. In this study, the influence of Ag and/or In doping on the microstructures and tensile properties of eutectic Sn-0.7Cu lead free solder alloy have been investigated. Also, the effects of temperature and strain rate on the mechanical performance of Sn-0.7Cu, Sn-0.7Cu-2Ag, Sn-0.7Cu-2In and Sn-0.7Cu-2Ag-2In solders were investigated. The tensile tests showed that while the ultimate tensile strength (UTS) and yield stress (YS) increased with increasing strain rate, they decreased with increasing temperature, showing strong strain rate and temperature dependence. The results also revealed that with the addition of Ag and In into Sn-0.7Cu, significant improvement in YS (∼255%) and UTS (∼215%) is realized when compared with the other commercially available Sn-0.7 wt. % Cu solder alloys. Furthermore, the Sn-0.7Cu-2Ag-2In solder material developed here also exhibits higher ductility and well-behaved mechanical performance than that of eutectic Sn-0.7Cu commercial solder. Microstructural analysis revealed that the origin of change in mechanical properties is attributed to smaller β-Sn dendrite grain dimensions and formation of new inter-metallic compounds (IMCs) in the ternary and quaternary alloys.     

Corrosion of cold-deformed brass in acid sulphate solution

The corrosion behaviour and the dezincification process of cold-deformed CuZn-42 brass were tested in an acid sulphate solution at pH-value 2 with additional chloride and copper(II) ions by use of the linear polarization method.The measured corrosion potential and densities of corrosion currents were observed as characteristics of the dezincification process and the corrosion resistance of tested samples of cold-deformed CuZn-42 brass. The results obtained have shown that pH-value 2 of the tested solutions and increased concentrations of copper(II) ions result in increased values of densities of corrosion currents of the tested brass samples, as a result of selective zinc dissolution and the individual dissolution of zinc and copper including the process of anodic oxidation. The tested concentrations of chloride ions in certain conditions have an inhibiting effect, whereas in the other conditions they act as distinctive activators of brass corrosion. The lowest values of corrosion currents are present in the brass samples with the highest deformation degree at 80%. The process of dezincification and anode dissolution of cold deformed brass samples were developed in the whole range of tested potentials.     

High-Temperature Oxidation of a Sn-Zn-Al Solder

The oxidation of 91Sn-9(95Zn-5Al) solder in theliquid state, 250°C, was studied by thermalgravimetric analysis (TGA). The oxidation behavior of63Sn-37Pb, 91Sn-9Zn, 99.4Sn-0.6Al, and Sn was alsoinvestigated for comparison. The weight gains per unitsurface area descend in the order: 63Sn-37Pb > Sn> 91Sn-9Zn > 91Sn-9(95Zn-5Al) > 99.4Sn-0.6Al.The initial weight gains of the materials investigated increase linearly with reaction time, whileparabolic behavior exists after the linear stage. Therate constants of the oxidation reaction for the tworeaction stages were determined. Activation energies for oxidation of the five materials weredetermined in the range of 250 to 400°C. Theactivation energies, derived from the linear rateconstants for the early stages of oxidation, are 27.7kJ/mole for 99.4Sn-0.6Al, 23.3 kJ/mole for 91Sn-9Zn, 21.4kJ/mole for 91Sn-9(95Zn-5Al), 20.5 kJ/mole for63Sn-37Pb, and 19.8 kJ/mole for Sn. Thesurface-oxidation behavior was investigated further withelectron spectroscopy for chemical analysis (ESCA) and Auger electronspectroscopy (AES). AES profiles showed that oxides ofZn and Al formed on 91Sn-9Zn and 91Sn-9(95Zn-5Al)solders, while tin oxide is formed on 63Sn-37Pbsolder.